The present invention relates to a dental instrument, in particular, an instrument for use in root canal therapy and more particularly in the final stages of root canal therapy during obturation of the root canal systems. In the latter instance, the instrument is capable of thermo-softening gutta percha in the root canal as well as searing off gutta percha in the root canal utilizing a controlled-temperature instrument.
At the present time, in root canal therapy, filling material such as gutta percha is inserted into the root canal and deformed, usually by the application of heat and pressure. The gutta percha is then able to flow into many irregularities of the prepared root canal, thus allowing for a three-dimensional obturation and sealing to occur. More specifically, when the gutta percha is softened, it is able to be compressed into the numerous aberrations of the root canal in order to effectively seal the root canal cavity.
The compressing of the gutta percha is performed by using a root canal filling spreader and filling condensors. Some prior art root canal spreader and filling condensers are made of stainless steel or nickel-chromium plated brass. The filling spreaders are smooth, flat-ended and slightly tapered. The conventional means for achieving a heated instrument tip is to heat the tip externally, for example, by holding the tip in a flame or in contact with a resistive heater. One disadvantage of this is that the instrument cools off quite rapidly. Thus, to overcome this and achieve the desired degree of heating at the end of the tip, it is often necessary to heat the tip until it glows. However, this increases the risk of accidental burns and tends to rapidly destroy the tip.
In the obturation of root canal systems during root canal therapy, it is usually necessary to sear off gutta percha, i.e., to apply heat to burn off unwanted filling material (excess gutta percha). This is often accomplished by introducing a dental instrument, such as a so-called plastic instrument, into an existing flame, such as that provided by a Bunsen burner, to heat the same and then applying the heated plastic instrument to the pulp chamber of the tooth having excess gutta percha. In this manner, excessive gutta percha is burned off so that only an amount of gutta percha necessary in the root canal is present. It should be recognized that although gutta percha is a commonly used substance to fill root canals, other deformable or heat moldable material are occasionally used to fill the root canals, but gutta percha will be used hereinafter as synonymous with a filling material for the purposes of this application.
There are several problems with this conventional method. First, the burning flame of the Bunsen burner is a hazard that may ignite other flammable material. Second, the flame must be kept constantly burning during the obturation of the root canal in view of the fact that it is used intermittently during the obturation procedure and it is not cost effective to continually extinguish and relight the flame. Third, the flame is often of such magnitude that it frightens patients (who may not be used to undergoing a dental procedure in the vicinity of a burning flame). Fourth, this obturation method requires frequent transfer of the heated dental instrument between the flame and the patient""s mouth. During such transfer(s), it is a continuous hazard that the instrument may inadvertently fall, burning something, more significantly and harmfully burning the mouth of the patient. Further, in view of the necessity of such transfer(s) between the flame and the patient""s mouth, there is an obvious loss of heat, i.e., the instrument cools somewhat after it is removed from the flame and before it is used operatively in the patient""s mouth. This loss of heat may be significant in view of the fact that the filling material, i.e., the gutta percha, will not melt if the instrument has cooled to a temperature below the melting temperature of the gutta percha.
In the prior art, the general endodontic process for filling a root canal in a tooth with gutta percha is described in U.S. Pat. No. 4,480,996 (Crovatto), U.S. Pat. No. 4,525,147 (Pitz et al.), U.S. Pat. No. 4,681,545 (Lapcevic), U.S. Pat. No. 4,894,011 (Johnson) and U.S. Pat. No. 5,067,900 (McSpadden).
U.S. Pat. No. 4,992,045 (Beisel) describes a self-contained heated root canal dental instrument which combines the operations of a root canal spreader, a root canal condenser and a root canal filling material beater. The instrument includes a frame and a heatable probe mounted to the frame and projecting outward therefrom. Heating means are arranged in connection with the frame for heating the probe. A battery is housed in the frame to provide power to the heating means. A switch is electrically coupled to an interposed between the heating means and the battery.
A similar type of instrument is the Endotec II(trademark) thermal condensor for gutta percha sold by Lone Star Technologies. This instrument is a cordless hand-piece with a quick-change top and enables a dentist to thermo-soften gutta percha in the root canal with a specially designed and shaped, electrically heated instrument tip. The amount of heat is purported to be precisely controllable by the dentist by depressing a heat activator button. Use of this instrument purports to provide the advantage of causing gutta percha to coalesce and fuse into a dense, homogeneous mass. Also, the gutta percha adapts to the shape of the root canal under pressure. A problem with this instrument is the fact that the tip is continuously exposed and uncovered and thus, when heated, can cause damage, e.g., burns to the dentist or patient.
Another inconvenience arises from the fact that the manufacturer suggests inserting the instrument tip into the root canal and then heating the probe by depressing the heat activator button. Although this avoids the problem of having a heated tip exposed before the actual procedure, it causes a delay in the treatment because the tip is only heated after it is inserted into the root canal and not before. Thus, the dentist must wait for the tip to be heated while in the root canal and then perform the necessary application of pressure to soften the gutta percha.
Accordingly, it is an object of the present invention to provide new and improved methods and apparatus for condensing root canal filling material and searing off gutta percha during the obturation phase of root canal therapy.
It is another object of the present invention to provide new and improved methods and apparatus for condensing root canal filling material and searing off gutta percha during the obturation phase of root canal therapy that are safe and effective.
It is yet another object of the present invention to provide new and improved methods and apparatus for condensing root canal filling material and searing off gutta percha during the obturation phase of root canal therapy which substantially avoid the problems with conventional methods and apparatus mentioned above.
It is still another object of the invention to provide a new and improved dental instrument that includes a metal component that is heatable in a safe manner and can be applied in a safe manner to conduct dental treatment in a patient""s mouth which requires the application of heat.
It is still another object of the present invention to provide a new and improved dental instrument that avoids the potentially obtrusive presence of a continually burning flame in proximity to the dental patient during dental procedures.
It is yet another object of the present invention to provide a new and improved instrument for condensing root canal filling material and searing off gutta percha during the obturation phase of root canal therapy which enables the instrument tip to be safely heated prior to insertion into a patient""s mouth.
It is still another object of the present invention to provide a new and improved dental instrument which includes a heatable tip which is heated while covered upon contact with a human hand, i.e., upon the application of pressure to the instrument.
Briefly, to accomplish at least some of these objectives, one embodiment of an apparatus for use in obturating a root canal in accordance with the invention comprises a first member comprising a frame, a heatable probe mounted to the frame to project outward from the frame and adapted for insertion into or into proximity of the root canal, and at least one pressure sensor for detecting application of external pressure on the first member, each pressure sensor being coupled to the heating probe such that the heating probe is heated upon the application of pressure on the first member. The apparatus also includes a second member for covering the heating probe, the second member being attachable to the first member in a position in which the second member covers the heating probe and movable from the position to expose the heating probe.
The second member may be a retractable cover connected to the first member and having a first position in which the cover covers the heating probe and a second retracted position in which the heating probe is exposed. Displacement means may thus be provided for enabling the cover to move between the first position and the second position. For example, the displacement means may be cooperating threads arranged on an outer periphery of the first member and on an inner surface of the cover. In the alternative, the second member may be a cover slidably connected to the first member such that the cover is slidable between a position in which the cover covers the heating probe and a position in which the heating probe is exposed. This cover may comprise axially extending channels and a respective slot at each end of each channel. The slots extending circumferentially around at least a portion of an inner surface of the cover. The first member includes projections at an upper end, each projection being slidable within a respective channel and slot associated with the channel.
If the first member is a cylindrical tube, the pressure sensor(s) may be arranged on an inner surface of the tube. In the alternative, the pressure sensor(s) may be embedded in a wall of the tube.
Heating means are arranged in connection with the frame for heating the heating probe and power means, e.g., a battery, are arranged in connection with the frame for providing power to the heating means. Control means control the heating means such that heating of the heating probe by the heating means is regulated. The control means are coupled to the pressure sensor(s) and direct the heating means to heat the heating probe when the application of external pressure on the first member is detected by the pressure sensor(s).
Another embodiment of an apparatus for use in obturating root canals comprises a cylindrical housing having an inwardly depressible region, a heatable probe adapted for insertion into or into proximity of the root canal, and a cradle having a seat in which the heating probe is received. The cradle is arranged inward of the depressible region of the housing and constructed such that depression of the region causes displacement of the cradle and movement of the heating probe in an outward direction. Heating means are arranged in the seat of the cradle and in engagement with the heating probe for heating the heating probe.
To activate the heating means, at least one pressure sensor is arranged on the housing for detecting application of external pressure on the housing. The pressure sensor(s) is/are coupled to the heating probe such that the heating probe is heated upon the application of pressure on the housing. Control means are thus also provided for controlling the heating means such that heating of the heating probe by the heating means is regulated. The control means are coupled to the pressure sensor(s) and direct the heating means to heat the heating probe when the application of external pressure on the housing is detected by one or more of the pressure sensors.
Another embodiment of the instrument in accordance with the invention comprises an elongate tube including electrically powered heating means and a curved heating probe coupled to the heating means, and a detachable cover for covering the heating probe of the tube when the heating probe is not in use. The heating means may be either a battery or other electricity storage module housed within the tube or an electric unit having a cord for connection to an external power source. When activated, the heating means function to heat the heating probe that extends at one end of the tube and curves slightly beyond that end of the tube. The cover releasably engages with one end of the tube and is designed to fit over the heating probe but not in contact therewith so that it is possible to heat the heating probe while it is still housed within the cover. The cover defines a space in an interior thereof in which the heating probe is situated and heated by the heating means upon energization thereof. Thus, upon detaching of the cover from its engagement with the tube, the probe has already been heated and is ready for use. On the other hand, after use of the heating probe, it is only necessary to place the cover into engagement with the end of the tube, at which time, the heating means can be turned off if desired. Alternatively, if the heating probe is to be re-used during the course of the dental treatment, the heating means can be maintained in an xe2x80x9con conditionxe2x80x9d.
Thus, one basic embodiment of an apparatus for obturating a root canal comprises a first member comprising a frame, and a heatable probe mounted to the frame to project outward from the frame and adapted for insertion into proximity of the root canal, and a second member for covering the heating probe. The second member is attachable to the first member in a position in which the second member covers the heating probe, and thereby prevents injury resulting from the heated probe, and is also movable from the position to expose the heating probe and enable use thereof. The first member may be a cylindrical tube and the second member a cover adapted to fit over the upper end of the cylindrical tube. To maximize the use of the heating probe for accessing the root canal, the heating probe preferably has a first portion extending parallel to axis of the first member and a second portion adjacent the first portion extending at an angle to the first portion. The thickness of the second portion, including its end, is dimensioned to enable entry into the root canal (the range of sizes of which is known to those skilled in the art) and thus has a very small thickness.
To heat the heating probe, heating means may be arranged in connection with the frame and powered by appropriate power means, either internal such as a battery housed in the frame, or appropriate electrical components to enable connection to a power cord connecting to an outlet. To maintain the temperature of the heating probe at a desired temperature, high enough to enable obturation, control means are provided for controlling the heating means, e.g., a switch electrically coupled to and interposed between the heating means and the power means.
In one embodiment, attachment means are provided for removably attaching the second member to the first member. The attachment means may comprise a first circumferentially extending snap arranged on an exterior surface of the first member and a second cooperating circumferentially extending snap arranged on an interior surface of the second member. Further, the attachment means preferably comprise recesses formed in a lower region of the first snap and projections formed in a lower region of the second snap.
In an enhanced embodiment, securing means are provided for securing the second member to the first member to prevent inadvertent separation of the second member from the first member.
In another embodiment, the second member is a retractable cover connected to the first member and has a first position in which the cover covers the heating probe and a second retracted position in which the heating probe is exposed. Displacement means are provided for enabling the second member to move between the first position and the second position. The displacement means may comprise cooperating threads arranged on an outer periphery of the first member and on an inner surface of the cover. Locking means may also be provided for locking the cover in the second position, e.g., a flexible, metal bracket arranged on an outer peripheral surface of the first member whereby one end of the bracket is attached to the outer surface of the first member and an opposite end of the bracket is free and displaceable by flexure toward and away from the outer surface such that at least a portion of the cover is insertable between the free end of the bracket and the outer surface of the first member. Biasing means such as a spring may also be provided for maintaining the cover in the first position.
In yet another embodiment, the second member is a cover slidably connected to the first member. The cover comprises axially extending channels and a respective slot at each end of each channel. The slots extend circumferentially around at least a portion of an inner surface of the cover. The first member includes projections at an upper end, each projection being slidable within a respective channel and slots associated therewith.
Another embodiment of the apparatus for obturating a root canal, comprises housing means defining an interior compartment, e.g., a tubular structure, a displaceable unit comprising a heatable probe adapted for insertion into proximity of the root canal, and heating means for heating the probe, and displacement means for moving the unit from a first position in which the probe is in the compartment to a second position in which the probe is outside of the compartment. The unit can include a frame on which the heating means and the probe are mounted and a battery coupled to the heating means for supplying power to the heating means. The displacement means may comprise an appendage attached to the unit and extending outside of the compartment, e.g., a circular disc and a shaft extending from the disc to the unit. Cooperating securing means are preferably arranged on the housing means and the unit for securing the unit in the first position in which the probe is exterior of the compartment and the second position in which the probe is inside the compartment.
Another similar embodiment of the instrument includes a pushbutton connected to the unit while the housing means including a slot having a pair of circular regions adapted to receive a spherical part of the pushbutton. The pushbutton further includes a rigid component connected to the unit and a spring interposed between the rigid component and the pushbutton.